Shaming people for flying won’t cut airline emissions. We need a smarter solution



Swedish airport operator Swedavia reported passenger numbers at its ten airports in October 2019 were down 5% on the previous year.
http://www.shutterstock.com

Duygu Yengin, University of Adelaide and Tracey Dodd, University of Adelaide

“Fake news”, the chief executive of Lufthansa has called it. But his counterpart at Air France calls it the airline industry’s “biggest challenge”. So does the president of Emirates: “It’s got to be dealt with.”

What they’re talking about is “flight shame” – the guilt caused by the environmental impacts of air travel. Specifically, the carbon emissions.

It’s the reason teen climate-change activist Greta Thunberg refused to fly to New York to address the United Nations Climate Action Summit in September, taking a 14-day sea voyage instead.

A publicity photo of Greta Thunberg on her way to New York aboard the yacht Malizia II in August 2019. The phrase ‘skolstrejk för klimatet’ means school strike for climate.
EPA

In Thunberg’s native Sweden, flight shame (“flygskam”) has really taken off, motivating people to not take off. Last year 23% of Swedes reduced their air travel to shrink their carbon footprint, according to a WWF survey. Swedish airport operator Swedavia reported passenger numbers at its ten airports in October were down 5% on the previous year.

The potency of this guilt is what put Lufthansa’s head, Carsten Spohr, on the defensive at an aviation industry conference in Berlin in November.




Read more:
Flight shame: flying less plays a small but positive part in tackling climate change


“Airlines should not have to be seen as a symbol of climate change. That’s just fake news,” he declared. “Our industry contributes 2.8% of global CO₂ emissions. As I’ve asked before, how about the other 97.2%? Are they contributing to global society with as much good as we do? Are they reducing emissions as much as we do?”

Does he have a point? Let’s consider the evidence.

How bad are aviation CO₂ emissions?

The International Council on Clean Transportation (the same organisation that exposed Volkwagen’s diesel emissions fraud), estimates commercial aviation accounted for 2.4% of all carbon emissions from fossil-fuel use in 2018.

So it’s true many other sectors contribute more.

It is also true airlines are making efforts to reduce the amount of carbon they emit per passenger per kilometre. Australia’s aviation industry, for example, has reduced its “emissions intensity” by 1.4% a year since 2013.

However, the ICCT estimates growth in passenger numbers, and therefore total flights, means total carbon emissions from commercial aviation have ballooned by 32% in five years, way faster than UN predictions. On that trajectory, the sector’s total emissions could triple by 2050.

Alternatives to fossil fuels

A revolution in aircraft design could mitigate that trajectory. The International Air Transport Association suggests the advent of hybrid electric aircraft propulsion (similar to how a hybrid car works, taking off and landing using electric power) by about 2030-35 could reduce fossil fuel consumption by up to 40%. Fully electric propulsion after that could eliminate fossil fuels completely.




Read more:
Get set for take-off in electric aircraft, the next transport disruption


Even with the advent of electric airliners by mid-century, the huge cost and long lifespan of commercial jets means it could still take decades to wean fleets off fossil fuels.

A shorter-term solution might be replacing fossil fuels with “sustainable aviation fuels” such as biofuels made from plant matter. But in 2018 just 15 million litres of aviation biofuel were produced – less than 0.1% of total aviation fuel consumption. The problem is it costs significantly more than standard kerosene-based aviation fuel. Greater use depends on the price coming down, or the price of fossil fuels going up.

Research into biofuels made from algae and other plant matter could prove a viable alternative to fossil fuels. Right now, though, cost is a major hurdle to uptake.
http://www.shutterstock.com

Pricing carbon

This brings us to the role of economics in decarbonising aviation.

An economist will tell you, for most goods the simplest way to reduce its consumption is to increase its price, or reduce the price of alternatives. This is the basis of all market-based solutions to reduce carbon emissions.

One way is to impose a tax on carbon, the same way taxes are levied on alcohol and tobacco, to deter consumption as well as to raise revenue to pay the costs use imposes on society.

The key problem with this approach is a government must guess at the price needed to achieve the desired reduction in demand. How the tax revenue is spent is also crucial to public acceptance.




Read more:
Why our carbon emission policies don’t work on air travel


In France, opposition to higher fuel taxes led the government to instead announce an “eco-tax” on flights.

This proposed tax will range from €1.50 (about A$2.40) for economy flights within the European Union to €18 (about A$29.30) for business-class flights out of the EU. Among those who think this price signal is too low to make any real difference is Sam Fankhauser, director of the Grantham Research Institute on Climate Change and the Environment in London.

Trading and offsets

Greater outcome certainty is the reason many economists champion an emissions trading scheme (also known as “cap and trade”). Whereas a tax seeks to reduce carbon emissions by raising the price of emission, a trading scheme sets a limit on emissions and leaves it to the market to work out the price that achieves it.

One advantage economists see in emissions trading is that it creates both disincentive and incentives. Emitters don’t pay a penalty to the government. They effectively pay other companies to achieve reductions on their behalf through the trade of “carbon credits”.

The European Union already has an emissions trading scheme that covers flights within the European Economic Area, but it has been criticised for limiting incentives for companies to reduce emissions because they can cheaply buy credits, such as from overseas projects such as tree-planting schemes.

Stockholm Arlanda Airport: Swedish data suggests voluntary action motivated by shame is unlikely to lead to any significant reduction in demand for international air travel.
http://www.shutterstock.com

This led to the paradox of scheme delivering a reported 100 million tonnes of “reductions/offsets” from Europe’s aviation sector between 2012 and 2018 even while the sector’s emissions increased.

A better solution might come from a well-designed international trading scheme. The basis for this may be the global agreement known as the Carbon Offsetting and Reduction Scheme for International Aviation. Already 81 countries, representing three-quarters of international aviation activity, have agreed to participate.




Read more:
Carbon offsets can do more environmental harm than good


What seems clear is that guilt and voluntary action to reduce carbon emissions has its limits. This is suggested by the data from Sweden, the heartland of flight shame.

Behind the 5% reduction in passenger numbers reported by Swedavia is a major difference between domestic passengers (down 10%) and international passengers (down just 2%). That might have something to do with the limited travel alternatives when crossing an ocean.

For most of us to consider emulating Greta Thunberg by taking a sailboat instead, the price of a flight would have to be very high indeed.The Conversation

Duygu Yengin, Associate Professor of Economics, University of Adelaide and Tracey Dodd, Research Fellow, Adelaide Business School, University of Adelaide

This article is republished from The Conversation under a Creative Commons license. Read the original article.

How indigenous expertise improves science: the curious case of shy lizards and deadly cane toads



File 20190408 2901 1tbo2ex.jpg?ixlib=rb 1.1
The Balanggarra Rangers are land management representatives of the Balanggarra people, the indigenous traditional owners of the East Kimberley. (L-R) Wes Alberts, Bob Smith (coordinator) James ‘Birdy’ Birch, Isiah Smith, Quentin Gore.
The Kimberley Land Council, Author provided

Georgia Ward-Fear, University of Sydney and Rick Shine, University of Sydney

It’s a common refrain – western ecologists should work closely with indigenous peoples, who have a unique knowledge of the ecosystems in their traditional lands.

But the rhetoric is strong on passion and weak on evidence.

Now, a project in the remote Kimberley area of northwestern Australia provides hard evidence that collaborating with Indigenous rangers can change the outcome of science from failure to success.




Read more:
We’ve cracked the cane toad genome, and that could help put the brakes on its invasion


Fighting a toxic invader

This research had a simple but ambitious aim: to develop new ways to save at-risk predators such as lizards and quolls from the devastating impacts of invasive cane toads.

Cane toads are invasive and highly toxic to Australia’s apex predators.
David Nelson

All across tropical Australia, the arrival of these gigantic alien toads has caused massive die-offs among meat-eating animals such as yellow-spotted monitors (large lizards in the varanid group) and quolls (meat-eating marsupials). Mistaking the new arrivals for edible frogs, animals that try to eat them are fatally poisoned by the toad’s powerful toxins.

Steep population declines in these predators ripple out through entire ecosystems.

But we can change that outcome. We expose predators to a small cane toad, big enough to make them ill but not to kill them. The predators learn fast, and ignore the larger (deadly) toads that arrive in their habitats a few weeks or months later. As a result, our trained predators survive, whereas their untrained siblings die.




Read more:
What is a waterless barrier and how could it slow cane toads?


Conservation ‘on Country’

But it’s not easy science. The site is remote and the climate is harsh.

We and our collaborators, the Western Australian Department of Biodiversity, Conservation and Attractions, decided at the outset that we needed to work closely with the Indigenous Traditional Owners of the east Kimberley – the Balanggarra people.

So as we cruised across the floodplain on quad bikes looking for goannas, each team consisted of a scientist (university-educated, and experienced in wildlife research) and a Balanggarra Indigenous ranger.

Although our study species is huge – a male yellow-spotted monitor can grow to more than 1.7 metres in length and weigh more than 6kg – the animals are well-camouflaged and difficult to find.

Over an 18-month study, we caught and radio-tracked more than 80 monitors, taught some of them not to eat toads, and then watched with trepidation as the cane toad invasion arrived.




Read more:
Yes, you heard right: more cane toads really can help us fight cane toads


Excitingly, the training worked. Half of our trained lizards were still alive by the end of the study, whereas all of the untrained lizards died soon after toads arrived.

That positive result has encouraged a consortium of scientists, government authorities, conservation groups, landowners and local businesses to implement aversion training on a massive scale (see www.canetoadcoalition.com), with support from the Australian Research Council.

A yellow-spotted monitor fitted with a radio transmitter in our study. This medium-sized male was trained and lived for the entirety of the study in high densities of cane toads.
Georgia Ward-Fear, University of Sydney



Read more:
Teaching reptiles to avoid cane toads earns top honour in PM’s science prizes


Cross-cultural collaboration key to success

But there’s a twist to the tale, a vindication of our decision to make the project truly collaborative.

When we looked in detail at our data, we realised that the monitor lizards found by Indigenous rangers were different to those found by western scientists. The rangers found shyer lizards, often further away from us when sighted, motionless, and in heavy cover where they were very difficult to see.

Gregory Johnson, Balanggarra elder and ranger.
Georgia Ward-Fear

We don’t know how much the extraordinary ability of the rangers to spot those well-concealed lizards was due to genetics or experience – but there’s no doubt they were superb at finding lizards that the scientists simply didn’t notice.

And reflecting the distinctive “personalities” of those ranger-located lizards, they were the ones that benefited the most from aversion training. Taking a cautious approach to life, a nasty illness after eating a small toad was enough to make them swear off toads thereafter.

In contrast, most of the lizards found by scientists were bold creatures. They learned quickly, but when a potential meal hopped across the floodplain a few months later, the goanna seized it before recalling its previous experience. And even holding a toad briefly in the mouth can be fatal.

Comparisons of conditions under which lizards were initially sighted in the field by scientists and Indigenous rangers (a) proximity to lizards in metres (b) density of ground-cover vegetation (>30cm high) surrounding the lizard (c) intensity of light directly on lizard (light or shade) (d) whether the lizard was stationary or moving (i.e. walking or running). Sighting was considered more difficult if lizards were further away, in more dense vegetation, in shade, and stationary.
Georgia Ward-Fear, University of Sydney

As a result of the intersection between indigenous abilities and lizard personalities, the overall success of our project increased as a result of our multicultural team.

If we had just used the conventional model – university researchers doing all of the work, indigenous people asked for permission but playing only a minor role – our project could have failed, and the major conservation initiative currently underway may have died an early death.

So our study, now published in Conservation Letters, provides an unusual insight – backed up by evidence.

Moving beyond lip service, and genuinely involving Indigenous Traditional Owners in conservation research, can make all the difference in the world.

Georgia Ward-Fear (holding a yellow-spotted monitor) with Balanggarra Rangers Herbert and Wesley Alberts.
David Pearson, WA Department of Biodiversity, Conservation and Attractions

This research was published in collaboration with James “Birdy” Birch and his team of Balanggarra rangers in the eastern Kimberley.The Conversation

Georgia Ward-Fear, Post doctoral fellow and Conservation Ecologist , University of Sydney and Rick Shine, Professor in Evolutionary Biology, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Why daily doses of nature in the city matter for people and the planet



File 20181120 161612 jduiq9.jpg?ixlib=rb 1.1
Brisbane’s South Bank parkland isn’t exactly getting out in the wild, but experiences of urban nature are important for building people’s connection to all living things.
Anne Cleary, Author provided

Anne Cleary, Griffith University

The environmental movement is shifting away from focusing solely on raising awareness about environmental issues. Many environmental agencies and organisations now also aim to connect people with nature, and our new research suggests daily doses of urban nature may be the key to this for the majority who live in cities.

Every year in the United Kingdom the Wildlife Trusts run the 30 Days Wild campaign. This encourages people to carry out a daily “random act of wildness” for the month of June. The International Union for Conservation of Nature recently launched its #NatureForAll program, which aims to inspire a love of nature.

This shift in focus is starting to appear in environmental policy. For example, the UK’s recent 25-year environment plan identifies connecting people with the environment as one of its six key areas. Similarly, in Australia, the state of Victoria’s Biodiversity 2037 plan aims to connect all Victorians to nature as one of two overarching objectives.

The thinking behind such efforts is simple: connecting people to nature will motivate them to act in ways that protect and care for nature. Evidence does suggest that people who have a high nature connection are likely to display pro-environmental attitudes and behaviours.

Looking beyond the park

What is less clear is how to enhance an individual’s nature connection – that is feeling that they are a part of nature. Over half of all people globally, and nine out of ten people in Australia, live in urban environments. This reduces their opportunities to experience and connect with nature.

Our new study may offer some answers. A survey of Brisbane residents showed that people who experienced nature during childhood or had regular contact with nature in their home and suburb were more likely to report feeling connected with nature.

The study used a broad definition of urban nature to include all the plants and animals that live in a city. When looking to connect urban residents with local nature we need to take a broad view and look “beyond the park”. All aspects of nature in the city offer a potential opportunity for people to experience nature and develop their sense of connection to it.

Raffles Place, Singapore – all urban nature should be seen as an opportunity for nature connection.
Anne Cleary, Author provided

The study also looked at the relationship between childhood and adult nature experiences. Results suggest that people who lack childhood experience of nature can still come to have a high sense of nature connection by experiencing nature as an adult.

There have been focused efforts on connecting children to nature, such as the Forest Schools and Nature Play programs. Equal effort should be given to promoting adult nature experiences and nature connection, particularly for people who lack such experiences.

The benefits of nature experience

We still have much to discover about how an individual’s nature connection is shaped. We need a better understanding of how people from diverse cultural and social contexts experience and connect to different types of nature. That said, we are starting to understand the important role that frequent local experiences of nature may play.

In addition to boosting people’s sense of nature connection, daily doses of urban nature deliver the benefits of improved physical, mental and social wellbeing. A growing evidence base is showing that exposure to nature, particularly in urban environments, can lead to healthier and happier city dwellers.

Robert Dunn and colleagues have already advocated for the importance of urban nature experiences as a way to bolster city residents’ support for conservation. They described the “pigeon paradox” whereby experiencing urban nature, which is often of low ecological value – such as interactions with non-native species – may have wider environmental benefits through people behaving in more environmentally conscious ways. They proposed that the future of conservation depended on city residents’ ability to experience urban nature.

As new evidence emerges we need to build on this thinking. It would seem that the future of our very connection to nature, our wellbeing and conservation depend on urban people’s ability to experience urban nature.The Conversation

The pigeon paradox: interactions with urban nature – here in London’s Hyde Park – may help make city dwellers more environmentally conscious.
Anne Cleary, Author provided

Anne Cleary, Research Fellow, School of Medicine, Griffith University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Why do dingoes attack people, and how can we prevent it?



File 20180725 194155 109dcyu.jpg?ixlib=rb 1.1
Dingoes are usually solitary, but can forage in groups near human settlements where food is abundant.
Klaasmer/Wikimedia Commons, CC BY-SA

Bill Bateman, Curtin University and Trish Fleming

The case of Debbie Rundle, who was attacked by dingoes at a mine site in Telfer, in Western Australia’s Pilbara region, evokes our instinctive horror at the idea of being attacked by wild animals.

Rundle suffered severe leg injuries in the incident, and said she feared she may have been killed had her colleagues not come to her aid.




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We know that there are carnivores throughout the world with the potential to kill us. And while most of us will never come face to face with a hungry wolf, lion, tiger or bear, such attacks do unfortunately still occur.

In the scale of things, such attacks are very uncommon – although that is little consolation to the victim. Australia’s dingoes are no exception; despite some infamous examples, dingo attacks on humans are mercifully rare. But people will still understandably want to know why they happen at all, and what can be done to prevent them.

Why do wild animals attack?

Research on wolf attacks shows that, absent the influence of rabies which can increase wolves’ aggression, two common factors associated with attacks are that they often happen in human-modified environments, and by animals that are habituated to human presence.

These two variables are obviously linked: many species of mammalian carnivore are highly adaptable, and soon learn that human settlements are sources of food, water and shelter.

These human resources can have a profound effect on the behaviour of wild animals. Abundant human food often reduces animals’ aggression towards one another, and can result in the presence of much larger numbers of individuals than normal.

This is equally true of dingoes. Although they are usually observed alone, it is not uncommon to see groups of ten or more dingoes foraging at rubbish dumps associated with mine sites in the Tanami Desert of central Australia. There are thought to be around 100 dingoes that forage in and around the Telfer mine where Rundle was attacked.

Waste food may inadvertently entice animals to human settlements, and this may lead to predators becoming habituated to human presence. In Canada, a young man fell victim to a wolf attack at a mine site; the local wolves were reported to be used to humans, and would even follow rubbish trucks to the tip. They may have come to associate human smells with the provision of food.

Animals that are habituated to humans lose some of their natural wariness towards them. This is typical of many animal species that adapt to urban habitats, and while this may be an appealing trait in squirrels or garden birds, it can be quite different if the animal is a predator capable of attacking a human.

Coyotes can be dangerous, especially when they get used to living in human environments.
Marya/Flickr/Wikimedia Commons, CC BY-SA

In the United States, there have been many reports of coyotes attacking humans. The coyote, like the dingo, is reasonably large (typically weighing 10–16kg) and can be found in close association with urban areas. The coyote’s natural range has expanded as wolves (their competitor) have dwindled, and their numbers have increased in and around cities where they find copious and consistent supplies of food and water.

A survey of reported attacks on humans by coyotes showed that many were “investigative”, often involving the animal trying to steal something they perceived as food from the person. Other attacks by coyotes could be identified as “predatory”, in which the victim was pursued and bitten, and often occurred when the coyotes were in a group.




Read more:
Dingoes do bark: why most dingo facts you think you know are wrong


The Telfer dingo attack similarly appears to have been investigative – a young dingo climbed onto a table and grabbed Rundle’s phone. But the incident turned nasty when Rundle (perhaps understandably) followed the dingo that had her phone; this seemed to trigger a defensive or predatory attack from two other dingoes.

On Queensland’s Fraser Island, more than half of the recorded aggressive incidents by dingoes towards humans happened when the person was walking or running, suggesting that a “chase” response may have been involved.

The Telfer site, like other mine sites, has strict rules about putting waste food in bins, and managers have been proactive in training workers to not feed dingoes, in an attempt to prevent just such attacks. Rundle certainly seems to have followed these rules.

Unfortunately, in her case, other variables contributed to the attack – an investigative approach by one dingo that stole an item (that may have smelled of food) seems to have turned into an aggressive group attack when she followed the animals.




Read more:
Want dingoes to leave people alone? Cut the junk food


What can we do to prevent such attacks? Mine site managers already do much to reduce the likelihood of such incidents by reducing dingoes’ access to food. Fencing off eating areas or storing food in cages – as is done at Fraser Island – can help in this regard.

Interestingly, many people believe that it is best not to act aggressively when they encounter a large carnivore, but in reality it depends on the species. For wolves and pumas, the best tactic seems to be to shout and throw objects to put them off.

The ConversationUltimately, the onus is on individual people to be aware of the potential danger of wild predators, and always to treat them with wariness and respect.

Bill Bateman, Senior Lecturer, Curtin University and Trish Fleming, Associate Professor

This article was originally published on The Conversation. Read the original article.

How does altitude affect the body and why does it affect people differently?



File 20180510 34006 1dsxxwq.jpg?ixlib=rb 1.1
How well you’ll cope on a mountain has little to do with how fit you are.
wynand van poortvliet unsplash, CC BY-SA

Brendan Scott, Murdoch University

Every year, thousands of people travel to high-altitude environments for tourism, adventure-seeking, or to train and compete in various sports. Unfortunately, these trips can be marred by the effects of acute altitude sickness, and the symptoms vary from person to person. To understand why people are affected differently, we have to look at how the body is affected by altitude.




Read more:
From Kilimanjaro to Everest: how fit do you have to be to climb a mountain?


How is ‘altitude’ different to sea level?

Air is comprised of different molecules, with nitrogen (79.04%) and oxygen (20.93%) making up the majority of each breath we take. This composition of air remains consistent, whether we are at sea level or at altitude.

However, with altitude, the “partial pressure” of oxygen in this air (how many molecules of oxygen are in a given volume of air) changes. At sea-level, the partial pressure of oxygen is 159 mmHg, whereas at 8,848m above sea level (the summit of Mt Everest), the partial pressure of oxygen is only 53 mmHg.

At high altitudes, oxygen molecules are further apart because there is less pressure to “push” them together. This effectively means there are fewer oxygen molecules in the same volume of air as we inhale. In scientific studies, this is often referred to as “hypoxia”.



Author provided/The Conversation, CC BY-ND

What happens in the body in high altitudes?

Within seconds of exposure to altitude, ventilation is increased, meaning we start trying to breathe more, as the body responds to less oxygen in each breath, and attempts to increase oxygen uptake. Despite this response, there’s still less oxygen throughout your circulatory system, meaning less oxygen reaches your muscles. This will obviously limit exercise performance.

Within the first few hours of altitude exposure, water loss also increases, which can result in dehydration. Altitude can also increase your metabolism while suppressing your appetite, meaning you’ll have to eat more than you feel like to maintain a neutral energy balance.

When people are exposed to altitude for several days or weeks, their bodies begin to adjust (called “acclimation”) to the low-oxygen environment. The increase in breathing that was initiated in the first few seconds of altitude exposure remains, and haemoglobin levels (the protein in our blood that carries oxygen) increase, along with the ratio of blood vessels to muscle mass.

Despite these adaptations in the body to compensate for hypoxic conditions, physical performance will always be worse at altitude than for the equivalent activity at sea level. The only exception to this is in very brief and powerful activities such as throwing or hitting a ball, which could be aided by the lack of air resistance.




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Tall tales misrepresent the real story behind Bhutan’s high altitude tigers


Why do only some people get altitude sickness?

Many people who ascend to moderate or high altitudes experience the effects of acute altitude sickness. Symptoms of this sickness typically begin 6-48 hours after the altitude exposure begins, and include headache, nausea, lethargy, dizziness and disturbed sleep.

These symptoms are more prevalent in people who ascend quickly to altitudes of above 2,500m, which is why many hikers are advised to climb slowly, particularly if they’ve not been to altitude before.

It’s difficult to predict who will be adversely affected by altitude exposure. Even in elite athletes, high levels of fitness are not protective for altitude sickness.

There’s some evidence those who experience the worst symptoms have a low ventilatory response to hypoxia. So just as some people aren’t great singers or footballers, some people’s bodies are just less able to cope with the reduction in oxygen in their systems.

There are also disorders that impact on the blood’s oxygen carrying capacity, such as thalassemia, which can increase the risk of symptoms.

But the best predictor of who may suffer from altitude sickness is a history of symptoms when being exposed to altitude previously.

How are high-altitude natives different?

People who reside at altitude are known to have greater capacity for physical work at altitude. For example, the Sherpas who reside in the mountainous regions of Nepal are renowned for their mountaineering prowess.

High-altitude natives exhibit large lung volumes and greater efficiency of oxygen transport to tissues, both at rest and during exercise.

While there is debate over whether these characteristics are genetic, or the result of altitude exposure throughout life, they provide high-altitude natives with a distinct advantage over lowlanders during activities in hypoxia.

The ConversationSo unless you’re a sherpa, it’s best to ascend slowly to give your body more time to adjust to the challenges of a hypoxic environment.

Brendan Scott, Senior Lecturer (S&C), Murdoch University

This article was originally published on The Conversation. Read the original article.

I’ve always wondered: why many people in Asian countries wear masks, and whether they work


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Face masks are a common sight in Asia. Why?
David Chang/AAP

C Raina MacIntyre, UNSW and Abrar Ahmad Chughtai, UNSW

This is an article from I’ve Always Wondered, a series where readers send in questions they’d like an expert to answer. Send your question to alwayswondered@theconversation.edu.au


In Japan, many people wear face masks – is that to prevent the wearer getting the infection, or is the wearer already infected and protecting those around? Is the mask useful in protecting against viruses or bacteria? – Petrina, Greenwich

Thanks for your question, Petrina. You’re right, in countries like Japan and China, facemask use in the community is widespread – much more so than in Western cultures. People wear them to protect the respiratory tract from pollution and infection, and to prevent the spread of any pathogens they might be carrying.

Whether this works depends on the type of mask.

There are three supposed ways a mask can provide protection: by providing a physical barrier (which prevents splashes and sprays), by filtering the particles (blocking particles of a certain size from entering the respiratory tract), and by fitting around the face to prevent leakage of air around the sides.

Some mask makers have also gone the extra step of using antimicrobials and claim to kill bugs on the surface of the mask, but these haven’t been tested to see if they provide any benefit.

Healthcare workers have been using cloth masks (made of cotton or other materials and with ties to secure them at the back) while caring for patients since the late 19th century to protect from various respiratory infections such as diphtheria, scarlet fever, measles, pandemic influenza, pneumonic plague and tuberculosis.

Cloth masks have been around since the late 19th century.
Author provided



Read more:
I’ve always wondered: why is the flu virus so much worse than the common cold virus?


During the mid 20th century, disposable surgical facemasks (similar in look to the cloth masks but made of paper) were developed. Surgical masks were developed to prevent the surgeon from contaminating the wound during surgery, but studies have not proven they help.

Surgical masks have no evidence of effectiveness.
from http://www.shutterstock.com

These were followed by respirators, which vary in shape and material but are designed to fit around the face and filter particles. Respirators are designed specifically to protect the respiratory tract from inhaled germs. There are many types, which may be reusable or disposable.

People must undergo fit-testing to ensure respirators are correctly fitted, with a good seal around the face. Unlike masks, respirators are subject to certification and regulation, and are proven to protect against respiratory infection.

Respirators are proven to protect against infection.
from http://www.shutterstock.com

Surgical masks are unregulated for filtration and do not fit around the face, and the evidence for their use is less convincing. In a community study, families with a sick child who wore such a mask were less likely to get sick if they also wore a mask, but many family members didn’t wear their masks all the time.

In a university setting, students were protected from sick classmates if they wore the mask within 36 hours of their classmate getting sick.

In many low income countries, the cost of even paper surgical masks is prohibitive, so cloth masks are used, washed and re-used. But these don’t protect against infection, and may even increase the risk of infection.

Prevention of infection vs source control

Masks can be used to protect healthy people (such as nurses and doctors) from exposure to infection, but are also used by sick people (such as a TB patient) to prevent spread of infections to others (called “source control”). There is less research on this use than on the use of masks by well people. The efficacy of source control is unknown.




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Do masks work?

It’s long been thought surgical masks protect from transmission of pathogens, which spread through the air on large, short-range droplets, while respirators protect against much smaller, airborne particles, which may remain suspended in the air for several hours and transmit infection over long distances. So most guidelines recommend a mask for droplet transmitting infections (such as influenza) and a respirator for airborne infections (such as TB and measles).

But we’ve shown respirators protect better than masks even against droplet-spread infections. And the longstanding belief that infections neatly fit into either droplet or airborne transmission is not correct. Respiratory transmission of infections is more complex than this.

To say whether masks work, we have to specify whether we’re talking about a respirator, a surgical mask or a cloth mask.

The respirators are the Rolls Royce option and do protect, and this is a tool for frontline health workers facing epidemics of known and unknown infections. Surgical masks probably also protect but to a lesser extent. But there’s no evidence cloth masks will protect against invading or escaping bugs.


The Conversation* Email your question to alwayswondered@theconversation.edu.au

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C Raina MacIntyre, Professor of Infectious Diseases Epidemiology, Head of the School of Public Health and Community Medicine, UNSW and Abrar Ahmad Chughtai, Epidemiologist, UNSW

This article was originally published on The Conversation. Read the original article.